1. Field of the Invention
This invention relates to a leakage-detecting device for sealed packages.
Also, this invention relates to a sealed container (including a sealed bag), which in the sealed state is used to store various items such as food, chemicals, batteries, and the like, and a method of detecting pinholes in that sealed container.
2. Description of the Related Art
Conventionally, sealed packages have been used as packages for food and the like in order to preserve freshness.
However, with these kinds of sealed packages, when there are pinholes, cracks, tears or the like, the sealing function is lost, however, inmost cases, the pinholes or cracks are very small and cannot be detected by visual inspection.
Therefore, attempts have been made to detect these kinds of pinholes or cracks by filling the sealed container with a detection gas for detecting leakage.
However, with the aforementioned prior technique, one or tens of sealed packages are taken to be an inspection unit, and leakage detection is performed for each detection unit (so called batch processing), so when leakage is found in one of the detection units, there was a problem in that all of the sealed packages of that detection unit had to be handled as being defective.
Taking this kind of prior problem into consideration, object (1) of this invention is to provide a leakage-detecting device for sealed packages that is capable of performing detection for all packages when performing leakage detection of the sealed packages.
As mentioned above, when there is a pinhole (small hole) in this kind of sealed container, it becomes easy for the stored contents such as food, chemicals or the like to react with air and to become spoiled or deteriorate, so in order to prevent this, it is necessary to inspect whether or not there are any pinholes in the container when shipping the product.
Conventionally, in order for this pinhole inspection, a method was performed in which helium gas was filled in the container along with the contents, and after the container was sealed (sealing process), inspection was performed using a gas detector for detecting whether or not there was helium gas leakage from the container.
In order to most efficiently perform the prior method mentioned above, it is preferred that the processes of filling the contents and helium into the container, sealing the container and detecting helium gas leakage after the container is sealed, be performed in a continuous product packaging line. However, in the case of the prior method, when filling the helium gas into the container together with the contents, a small amount of helium gas may leak outside of the container. In that case, the concentration of gas inside each of the containers to be inspected is not constant, and accurate inspection cannot be performed. Also, since helium gas is highly diffusible and mixes easily in the surrounding air, the gas detector reacts with the helium gas that leaked out during filling, and in that case, it is difficult to distinguish gas leakage after filling. Particularly, a high-performance gas detector reacts with even minute amounts of gas, so it reacts during filling even when there is only very little gas leakage. Therefore, a high-performance gas detector cannot be used.
From the above situation, in order to accurately inspect gas leakage after filling, the process of filling the helium gas and sealing the container must be performed in a different location than the process after that of inspecting for gas leakage. Also, supposing that there is a pinhole in a sealed container and that there is gas leakage, a large amount of gas leaks out while moving to the inspection process, and accurate inspection may not be possible. Furthermore, in the case of a large pinhole, all of the gas will leak out before inspection, and inspection becomes impossible. Moreover, this is also not preferred from an aspect of cost since expensive inspection gas is wasted.
This invention was devised to solve the weaknesses in the prior technology described above, object (2) of this invention is to provide a sealed container for which it is possible to accurately perform pinhole inspection (gas leakage inspection) using a small amount of inspection gas, and for which the process of filling the contents and inspection gas can be performed continuously in the same place as the pinhole inspection process, and to provide a pinhole-detection method that uses that sealed container.